Meet the biology major evolving the Heroes of the Storm A.I. to combo you to death

Blizzard EntertainmentFebruary 7, 2020

Senior Designer Kevin Gu takes great joy in moments when the Heroes of the Storm A.I. dunks on him during playtests. Maybe a little too much joy.

“When you get annihilated by Diablo Shadow Charging you into a wall, stunning you, popping Apocalypse, and then flipping you back into the Apocalypse,” says Gu, “you think ‘oh my goodness, I just got destroyed by the A.I.’”

But to reliably capitalize on human mistakes like that, you first have to get the A.I. into position to do so. That’s the challenge Gu, who got involved with A.I. on the Heroes team three years ago, is currently focused on. The current system holds two major components: the Goal system and the Tactical system. Put simply, the Goal system decides where the Hero moves, and the Tactical system determines what they do when they get there. These two systems interact with each other to drive A.I. behavior.

“Before, [the A.I.] would often get confused about where they should go,” says Gu.

This confusion was the result of conflict between the Goal and Tactical systems.

“You had two systems fighting the A.I. on where they should go… one on its left shoulder and one on its right,” Gu says.

He raises his fists and shakes them in opposite directions. “‘’Go here! No, go here!’ It’s like giving Cho and Gall each control of one leg!”

What kind of situation would trigger an argument like that?

“The Goal system would be saying ‘I need you to go to this objective because our team needs you to be there,’” Gu says. “Then the Tactical system would be saying ‘Oh, that’s cool, but I need you to stand here because this is the most optimal place for combat.’”

Gu says the troubles began about a year ago when the team tried to make the A.I. smarter individually.

“[The A.I.] no longer wanted to do things together,” says Gu. “Instead they wanted to do things by themselves.”

That was a problem, especially in Heroes of the Storm, which emphasizes teamplay above all else. As of the latest update, this value is now reflected in how the A.I. plays. Gu and the team detangled the two systems to make them more independent, allowing the A.I. to make better gameplay decisions for the team overall. That means no more inner voices arguing inside the Heroes A.I.

Gu hopes that by teaching the Heroes A.I. to play nice together, he can help teach players to work together too. Along with building bots that are fun to play against, educating players is one of the A.I. team’s main goals.

“Kerrigan is a really good example. One of her powerful moments is grasping people toward her and stunning them. We try our best to put those moments into the A.I. so they can perform it, too. Then the player sees it and says ‘oh, wow, that’s really cool, I didn’t know she could do that. That’s a combo I could be doing.’”

Gu’s been working toward building powerful moments like that for a long time. He started at Blizzard on the User Experience team eight years ago, where he playtested and wrote feedback to the dev teams on a number of IPs. It was an unexpected development for him, since he’d studied something totally different in college.

“I actually have a biology major. I loved video games, but never planned on making them—it wasn’t until I took a chance and got totally hooked. I was interested in physical therapy.”

The truth was that he liked working with people and solving tough problems. Heroes of the Storm A.I. is certainly that, and Gu is excited to continue improving it and making the A.I. the best role models they can be.

To read more about the details of the latest update to the Heroes A.I., check out Kevin Gu’s forum post. Good luck and have fun in your next Versus A.I. match!

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